Study will determine if platelet concentrates, currently stored for 7 days after phlebotomy, can be stored up to 10 days by preventing pH fall in the units, by addition of bicarbonate 5 days after phlebotomy. Methodology used will be autologous reinfusion of 51 Chromium-labelled platelets in NV donors. Comparison of recovery and survival of the platelets in the circulation will determine if the hypothesis is established.